Intracellular calcium metabolism and cellular calcium transport will be studied in isolated cells and in subcellular systems. The role of the mitochondria in controlling and regulating cytoplasmic calcium and cellular function will be investigated by kinetic analyses of Ca-45 movements in isolated cells and in isolated mitochondria. The ionic influences of phosphate, Na, H, Mg ions on cell calcium homeostasis will be investigated as well as the hormonal effects of parathyroid hormone, calcitonin, the metabolites of cholecalciferol, adrenal steroids and oestrogens. The role of cyclic AMP as a regular of calcium homeostasis will be studied in relation to cellular hormone action, stimulus secretion coupling and to the regulation of cardiac contractility under the influence of catecholamines. A computer model of cellular calcium homeostasis will be designed from the data gathered, and the influence of ions and hormones will be simulated to test the validity of many hypotheses previously offered, the site of action of stimuli, the overall interrelationship among cellular compartments and the regulation of cellular calcium transport.